A combined rectangular cavity broadband wave-absorbing structure loaded with a graded metal strip array

Abstract

The application discloses a combined rectangular cavity broadband wave-absorbing structure loaded with a gradient metal strip array, wherein the wave-absorbing structure is composed of a plurality of wave-absorbing units arranged in sequence, and each wave-absorbing unit comprises four rectangular cavities with different sizes, a gradient metal strip array and NDDP3 wave-absorbing material; the four rectangular cavities with different sizes are arranged in sequence according to the size; the NDDP3 wave-absorbing material is impregnated on the surfaces of the four rectangular cavities; and the gradient metal strip array is loaded on the four sides of three rectangular cavities with smaller sizes respectively. The different sizes of the rectangular cavities are combined to widen the absorption bandwidth of the wave-absorbing body, and the gradient metal strip array is loaded to compensate for the poor wave-absorbing performance of the combined rectangular cavities at a low frequency band; the application has good wave-absorbing performance in a 2-40GHz frequency band, and still has a wide wave-absorbing bandwidth under large-angle oblique incidence.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electromagnetic wave absorption, and particularly relates to a combined rectangular cavity broadband wave absorption structure loaded with a gradually changing metal strip array. BACKGROUND

[0002] Structural wave absorption material is a multifunctional composite material which can not only be used as a structural member to bear load, but also has good electromagnetic wave absorption or transmission capacity. Such material combines the advantages of light weight and high strength of composite materials, and shows broad application prospects in the fields of modern electronic countermeasures and military stealth.

[0003] However, structural wave absorption material often has a narrow absorption frequency band, has high efficient electromagnetic wave absorption capacity only in a specific frequency range, and has poor absorption effect in other frequency bands. Moreover, the wave absorption performance under large-angle oblique incidence of electromagnetic waves is rarely considered. In order to solve the above problems, the application provides a combined rectangular cavity broadband wave absorption structure loaded with a gradually changing metal strip array. SUMMARY

[0004] The application aims to solve the problems of the prior art, and provides the following scheme:

[0005] A combined rectangular cavity broadband wave absorption structure loaded with a gradually changing metal strip array, wherein the wave absorption structure is composed of a plurality of wave absorption units arranged in sequence, and each wave absorption unit comprises four rectangular cavities with different sizes, a gradually changing metal strip array and NDDP3 wave absorption material.

[0006] The four rectangular cavities with different sizes are arranged in sequence according to the size.

[0007] The NDDP3 wave absorption material is impregnated on the surfaces of the four rectangular cavities.

[0008] The gradually changing metal strip array is loaded on the four sides of the three rectangular cavities with smaller sizes.

[0009] Preferably, the material of the rectangular cavities is light-cured resin.

[0010] Preferably, the four rectangular cavities with different sizes comprise a first rectangular cavity, a second rectangular cavity, a third rectangular cavity and a fourth rectangular cavity.

[0011] The first rectangular cavity has a height of h1, a width of a1 and a length of b1.

[0012] The second rectangular cavity has a height of h2, a width of a2 and a length of b2.

[0013] The third rectangular cavity has a height of h3, a width of a3 and a length of b3.

[0014] The fourth rectangular cavity has a height h4, a width a4 and a length b4.

[0015] h1>h2>h3>h4, a1>a2>a3>a4, b1>b2>b3>b4.

[0016] Preferably, the thickness of the NDDP3 wave-absorbing material is 1mm.

[0017] Preferably, the gradient metal strip array is loaded on the four sides of the second rectangular cavity, the third rectangular cavity and the fourth rectangular cavity, respectively.

[0018] Preferably, the gradient metal strip array is composed of a plurality of metal strips with different lengths.

[0019] The widths of the plurality of metal strips are the same, and the spacing distances between the plurality of metal strips are the same.

[0020] The metal strips on each rectangular cavity are arranged in length gradient from short to long.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] The present application combines rectangular cavities with different sizes and loads a gradient metal array, so that the structure has good wave-absorbing performance in the frequency range of 2-40GHz. Under the condition of electromagnetic wave oblique incidence, the structure is a three-dimensional superstructure, and under the condition of electromagnetic wave oblique incidence, the electromagnetic wave will be scattered when it enters the side of the combined rectangular cavity, so that the structure still has a very wide wave-absorbing bandwidth under the condition of large incidence angle. The present application is made by light-curing 3D printing, which is simpler to make than traditional wave-absorbing materials, and the light-curing resin has high hardness, so the mechanical strength of the structure is high. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the present application, the following briefly introduces the drawings needed in the embodiments. Obviously, the drawings described in the following are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0024] Figure 1 It is a schematic diagram of the wave-absorbing structure of the embodiment of the present application.

[0025] Figure 2 It is a schematic diagram of the wave-absorbing unit of the embodiment of the present application.

[0026] Figure 3 It is a side view of the wave-absorbing unit of the embodiment of the present application.

[0027] Figure 4 A top view of the absorbing unit of the embodiment of the present application;

[0028] Figure 5 A size diagram of the gradient metal strip array of the embodiment of the present application;

[0029] Figure 6 A comparison diagram of the reflectivity under the vertical incidence angle of the combined rectangular cavity broadband absorbing structure loaded with the gradient metal strip array and the combined rectangular cavity broadband absorbing structure not loaded with the gradient metal strip array, wherein a is the reflectivity comparison diagram under the TE polarization, and b is the reflectivity comparison diagram under the TM polarization;

[0030] Figure 7 A schematic diagram of the electromagnetic wave in which the electric field is incident to the gradient metal strip array and an equivalent circuit diagram of the gradient metal strip array of the embodiment of the present application;

[0031] Figure 8 A schematic diagram of the interference cancellation model of the embodiment of the present application;

[0032] Figure 9 A diagram of the reflectivity under different incidence angles of the combined rectangular cavity broadband absorbing structure loaded with the gradient metal strip array with respect to the frequency, wherein a is the reflectivity with respect to the frequency under the TE polarization, and b is the reflectivity with respect to the frequency under the TM polarization. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0034] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0035] Embodiment one

[0036] In the present embodiment, a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array is provided. The absorbing structure is composed of a plurality of absorbing units arranged in sequence. Each absorbing unit comprises four rectangular cavities with different sizes, a gradient metal strip array and NDDP3 absorbing material. The four rectangular cavities are arranged in sequence according to the size. The NDDP3 absorbing material is impregnated on the surface of the four rectangular cavities. The gradient metal strip array is loaded on the four sides of the three rectangular cavities with smaller sizes. The material of the rectangular cavities is selected from photocurable resin. The thickness of the NDDP3 absorbing material is 1 mm.

[0037] The four rectangular cavities with different sizes include a first rectangular cavity, a second rectangular cavity, a third rectangular cavity, and a fourth rectangular cavity; the first rectangular cavity has a height of h1, a width of a1, and a length of b1; the second rectangular cavity has a height of h2, a width of a2, and a length of b2; the third rectangular cavity has a height of h3, a width of a3, and a length of b3; and the fourth rectangular cavity has a height of h4, a width of a4, and a length of b4. h1 > h2 > h3 > h4, a1 > a2 > a3 > a4, and b1 > b2 > b3 > b4.

[0038] The gradient metal strip array is loaded on the four sides of the second rectangular cavity, the third rectangular cavity, and the fourth rectangular cavity. The gradient metal strip array is composed of a plurality of metal strips with different lengths; the widths of the plurality of metal strips are the same, and the spacing distances between the plurality of metal strips are the same; and the metal strips on each rectangular cavity are arranged in length gradient from short to long.

[0039] Embodiment two

[0040] In this embodiment, as shown in Figure 1 , a combined rectangular cavity broadband wave-absorbing structure loaded with a gradient metal strip array is composed of nine wave-absorbing units arranged in sequence.

[0041] The wave-absorbing unit, as shown in Figure 2 , includes four rectangular cavities with different sizes, a gradient metal strip array, and NDDP3 wave-absorbing material. The four rectangular cavities with different sizes are arranged in sequence according to the size; the NDDP3 wave-absorbing material is impregnated on the surface of the four rectangular cavities; and the gradient metal strip array is loaded on the four sides of the three rectangular cavities with smaller sizes. The material of the rectangular cavity is selected from photocuring resin and is made by a photocuring printer. The thickness of the NDDP3 wave-absorbing material is t = 1 mm.

[0042] As shown in Figure 2 , Figure 3 , Figure 4 , the four rectangular cavities with different sizes include a first rectangular cavity, a second rectangular cavity, a third rectangular cavity, and a fourth rectangular cavity; the first rectangular cavity has a height of h1 = 10 mm, a width of a1 = 12 mm, and a length of b1 = 12 mm; the second rectangular cavity has a height of h2 = 8 mm, a width of a2 = 8 mm, and a length of b2 = 10 mm; the third rectangular cavity has a height of h3 = 6 mm, a width of a3 = 6 mm, and a length of b3 = 8 mm; and the fourth rectangular cavity has a height of h4 = 4 mm, a width of a4 = 4 mm, and a length of b4 = 6 mm.

[0043] As shown in Figure 5As shown, the gradually changing metal strip array is loaded on the four sides of the second, third and fourth rectangular cavities. The gradually changing metal strip array is composed of metal strips with different lengths; the widths of the metal strips are the same, w=0.3 mm, and the spacing distances between the metal strips are the same, s=0.5 mm; the metal strips on each rectangular cavity are arranged in length from short to long, L1=10 mm, L2=9 mm, L3=8 mm, L4=7 mm, L5=6 mm, L6=5 mm, L7=4 mm, L8=3 mm, L9=2 mm, L10=1 mm, L11=8 mm, L12=7 mm, L13=6 mm, L14=5 mm, L15=4 mm, L16=3 mm, L17=2 mm, L18=6 mm, L19=5 mm, L20=4 mm, L21=3 mm, L22=2 mm.

[0044] Example Three

[0045] In this embodiment, the comparison chart of TE polarization and TM polarization reflectivity of the combined rectangular cavity broadband wave-absorbing structure loaded with the gradually changing metal strip array and not loaded with the gradually changing metal strip array at the vertical incidence angle is as shown in Figure 6 (a), Figure 6 (b) can be seen that the difference in wave-absorbing performance of the combined rectangular cavity is not large whether the gradually changing metal strip array is loaded or not in the 6-40 GHz frequency band, because the electric field is parallel to the long side direction of the metal strip when the electromagnetic wave is vertically incident to the gradually changing metal strip array, as shown in Figure 7 When the electric field component direction of the incident electromagnetic wave is parallel to the metal strip grid, the electrons on the strip grid will accelerate due to the electric field force, and when the electric field direction changes, the speed of the electrons is the largest, because the limitation of the metal strip grid on the spatial movement distance of the electrons is relatively reduced a lot, and when the low-frequency electromagnetic wave is incident, the electrons can accelerate in the same direction for a relatively long time, thus obtaining a relatively large kinetic energy. That is, the lower the frequency of the incident electromagnetic wave, the more electromagnetic energy the electrons can consume, and the weaker the transmission ability of the incident electromagnetic wave. When the high-frequency electromagnetic wave is incident, the direction of the electric field component of the incident electromagnetic wave changes relatively quickly, the acceleration time of the electrons is relatively short, the kinetic energy obtained is small, and the electromagnetic energy consumed by the electrons is relatively small, so the incident electromagnetic wave has a relatively high transmission ability. Therefore, when the electric field direction of the incident electromagnetic wave is parallel to the metal strip grid structure, the filtering characteristic of the metal strip grid structure is high-pass, and the metal strip array structure is inductive at this time. As shown in Figure 7As shown in the metal array in this case is equivalent modeling, in the equivalent circuit, from the incident end to the exit end can pass through the high frequency signal current, the current of low frequency signal will flow into the ground inductance, equivalent to a high pass filter. Therefore for high frequency electromagnetic wave, the gradient metal array has less energy loss, when the high frequency electromagnetic wave is incident to the metal strip surface will be transmitted through the metal strip to the combined rectangular cavity inside, electromagnetic wave is mainly through the combined rectangular cavity energy loss, so in 6-40GHz frequency band, whether to load gradient metal strip array, the combined rectangular cavity wave absorption performance gap is not big.

[0046] In 2-6GHz frequency band as shown in Figure 6 , loading gradient metal strip array than not loading gradient metal strip array wave absorption performance has a significant improvement, the reason is that when the low frequency electromagnetic wave is incident to the metal strip surface, under the action of electric field, the electrons in the metal strip will move at high speed to consume electromagnetic wave energy. And why choose different length of metal strip combination to form metal strip array, because for different length of metal strip, its absorption peak corresponding to the frequency point is different, and the shorter the length of the metal strip, the higher the frequency point corresponding to the absorption peak, therefore. When a plurality of different length of metal strip combination, different resonance frequency absorption peak will be formed by the collection of wideband, so as to realize the wideband absorption of electromagnetic wave.

[0047] According to the above analysis in 6-40GHz frequency band electromagnetic wave is mainly by the combined rectangular cavity structure wave absorption. As shown in Figure 6 , in 6-40GHz frequency band the structure still has good wave absorption performance. In 6-40GHz frequency band, the combined rectangular cavity for its wave absorption mainly through the following three ways:

[0048] The first is that the electromagnetic wave is incident to the rectangular cavity through the rectangular cavity surface after the wave absorption material NDDP3, electromagnetic wave in the form of electromagnetic loss is dissipated, NDDP3 is a kind of magnetic loss material, which can effectively absorb electromagnetic wave. When the electromagnetic wave is incident to NDDP3, due to the magnetic induction effect will produce induced current in NDDP3, and then lead to the generation of eddy current, eddy current flow in the material, will the energy of incident electromagnetic wave into heat and consume, this kind of loss is called eddy current loss; in addition, the magnetic domain wall movement and rotation in NDDP3 can not keep up with the change of the applied magnetic field, resulting in the change of magnetic induction intensity lags behind the change of the applied magnetic field. This lag phenomenon will make part of the incident electromagnetic wave energy loss in the form of heat, namely magnetic hysteresis loss;

[0049] In addition to the above two kinds of loss, when the electromagnetic field is incident to NDDP3, the relaxation process in the magnetization process will also cause loss, these relaxation processes include the accelerated motion of domain wall, the consumption of elastic energy, magnetic aftereffect, etc.

[0050] The second part is that the reflection wave of the electromagnetic wave incident to the surface of the structure and the wave incident to the inside of the structure and propagated to the surface of the structure after being reflected by the metal backing plate at the bottom of the structure interfere with each other and are reduced in the form of interference loss. Figure 8 As shown in the interference cancellation model, the interference loss mechanism of the combined rectangular cavity can be explained. When a column of electromagnetic waves propagates in the air to the surface of the wave absorber, part of the energy will be reflected at the front interface (denoted as R1), and the remaining energy will penetrate the front interface into the inside of the lossy medium and continue to propagate, and after being reflected by the metal backing plate, it will be finally reflected to the air through the front interface (denoted as R2). The two reflected waves will meet at the front interface, at which time the phase difference between R1 and R2 depends on the optical path difference of the two waves, that is, twice the thickness of the wave absorbing material:

[0051]

[0052] where d represents the thickness of the wave absorber, λ represents the wavelength of the electromagnetic wave, f represents the frequency of the electromagnetic wave, c represents the speed of light, μ represents the magnetic permeability of the wave absorber, and ε represents the dielectric constant of the wave absorber. If the phase difference of the two reflected waves is exactly equal to an odd number of 180 degrees (that is, ), the two waves interfere with each other and the total reflected wave intensity reaches the weakest, that is, a strong reflection loss peak occurs.

[0053] The third part is that the electromagnetic wave incident to the side surface of the rectangular cavity is reflected multiple times and is finally reduced in the form of scattering loss. Since the combined rectangular cavity is a kind of 3D superstructure wave absorber, it has non-uniformity in structure, which enables the combined rectangular cavity to effectively interact with electromagnetic waves, resulting in scattering of electromagnetic waves during propagation. This scattering causes the energy of the electromagnetic wave to be dispersed in the medium, increasing the interaction opportunities between the electromagnetic wave and the material, so as to loss the energy of the electromagnetic wave.

[0054] The embodiment of the present application proposes a combined rectangular cavity broadband wave absorbing structure loaded with a gradually changing metal strip array, which still has a wide wave absorbing bandwidth under large-angle oblique incidence, which is similar to the scattering loss mechanism of the combined rectangular cavity in the 6-40GHz frequency band. Under the condition of oblique incidence of electromagnetic waves, the electromagnetic waves incident to the side surface of the combined rectangular cavity will be scattered, so that the structure still has a very wide wave absorbing bandwidth under a large incidence angle. Figure 9 As shown in the figure, the combined rectangular cavity broadband wave absorbing structure loaded with a gradually changing metal strip array in the embodiment of the present application has good wave absorbing performance under the condition of 50° incidence angle.

[0055] In addition, the embodiment of the present application proposes a combined rectangular cavity broadband wave-absorbing structure loaded with a gradient metal strip array. Since the combined rectangular cavity is made by light-cured 3D printing, compared with traditional wave-absorbing materials, the combined rectangular cavity is relatively simple to make. Meanwhile, since the light-cured resin has high hardness, the mechanical strength of the structure is high.

[0056] The above-described embodiments are only descriptions of the preferred modes of the present application and are not intended to limit the scope of the present application. Various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art without departing from the design spirit of the present application shall fall within the protection scope of the present application defined by the claims.

Claims

1. A combined rectangular cavity broadband wave-absorbing structure loaded with a graded metal strip array, characterized in that, The wave-absorbing structure is composed of a plurality of wave-absorbing units arranged in sequence, and each wave-absorbing unit comprises four rectangular cavities with different sizes, a gradient metal strip array and a wave-absorbing material. The four rectangular cavities with different sizes are arranged in sequence according to the size. The wave-absorbing material is impregnated on the surface of the four rectangular cavities. The gradient metal strip array is loaded on the four sides of the three rectangular cavities with smaller sizes, respectively. The four rectangular cavities with different sizes comprise a first rectangular cavity, a second rectangular cavity, a third rectangular cavity and a fourth rectangular cavity. The height of the first rectangular cavity is h1, the width is a1, and the length is b1. The height of the second rectangular cavity is h2, the width is a2, and the length is b2. The height of the third rectangular cavity is h3, the width is a3, and the length is b3. The height of the fourth rectangular cavity is h4, the width is a4, and the length is b4. Wherein, h1 > h2 > h3 > h4, a1 > a2 > a3 > a4, b1 > b2 > b3 > b4.

2. The combined rectangular cavity broadband wave-absorbing structure loaded with the array of gradient metal strips according to claim 1, characterized in that, The material of the rectangular cavity is selected from photocurable resin.

3. The combined rectangular cavity broadband wave-absorbing structure loaded with a gradient metal strip array according to claim 1, characterized in that, The height of the first rectangular cavity is h1 = 10 mm, the width is a1 = 12 mm, and the length is b1 = 12 mm. The height of the second rectangular cavity is h2 = 8 mm, the width is a2 = 8 mm, and the length is b2 = 10 mm. The height of the third rectangular cavity is h3 = 6 mm, the width is a3 = 6 mm, and the length is b3 = 8 mm. The height of the fourth rectangular cavity is h4 = 4 mm, the width is a4 = 4 mm, and the length is b4 = 6 mm.

4. The combined rectangular cavity broadband wave-absorbing structure loaded with the array of gradient metal strips according to claim 1, characterized in that, The thickness of the wave-absorbing material is t = 1 mm.

5. The combined rectangular cavity broadband wave-absorbing structure loaded with the array of gradient metal strips according to claim 1, characterized in that, The gradient metal strip array is loaded on the four sides of the second rectangular cavity, the third rectangular cavity and the fourth rectangular cavity, respectively.

6. The combined rectangular cavity broadband wave-absorbing structure loaded with the array of gradient metal strips according to claim 1, characterized in that, The gradient metal strip array is composed of a plurality of metal strips with different lengths. The widths of the plurality of metal strips are the same, and the spacing distances between the plurality of metal strips are the same. The metal strips on each rectangular cavity are arranged in sequence from short to long according to the length gradient.

Images